Pyrazolyltriazole herbicides

ABSTRACT

The invention is novel 4-(pyrazolyl)-4H-1,2,4-triazoles, the preparation thereof including their salts, and a method for controlling undesirable plant species therewith.

This is a division of application Ser. No. 619,982, filed Oct. 6, 1975,pending.

SUMMARY OF THE INVENTION

The invention is compounds of the formula: ##STR1## wherein R₁ ishydrogen, alkyl (C₁ -C₃), benzyl, acyl (C₂ -C₄) or N-alkyl (C₁ -C₃)carboxamido; R₂ is hydrogen, methyl or phenyl; R₃ is methyl or ##STR2##wherein X is hydrogen, halogen, alkyl (C₁ -C₃) or trifluoromethyl; oracid addition salts of the compounds. The invention includes a methodfor preparing the compounds and a method for controlling undesirableplant species therewith.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to herbicidal pyrazolyltriazole.

2. Description of the Prior Art

Prior art is as follows. Triazolylpyrazoles, Fedotova, A. P.; Kazymov,A. V.; Shchelkina, E. P. (All Union Scientific-Research Institute of thePhotographic Chemical Industry) U.S.S.R. 245, 554 (1969). HeterocyclicCompounds from Urea Derivatives, Kurzer, Frederick and Douraghi-Zadeh,K.; J. Chem. Soc. p. 3912-3922 (1965). Heterocyclic Compounds from UreaDerivatives, Kurzer, Frederick and Douraghi-Zadeh, K.; J. Chem. Soc. P.4448-4455 (1965). Syntheses and Reactions of5-Alkyl-4-Amino-3-Hydrazino-s-Triazoles, Takimoto, H. H., Denault, G. C.and Hotta, S.; J. Org. Chem. 30:711-713 (1965).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

4-Pyrazolyl-4H-1,2,4-triazole exists as a tautomeric isomer, asillustrated below: ##STR3##

Structure determinations by x-ray crystallographic analysis indicatethat the two tautomers Ia and Ib are present in an approximately 50:50ratio.

The novel derivatives of the above compound (Ia⃡Ib), comprise thecompounds of the present invention and are graphically illustrated asfollows: ##STR4##

Since the tautomers IIa⃡IIb also exist in approximately 50:50 ratios (asconfirmed by x-ray crystallographic analysis), numerical structureassignment is arbitrary, and in the present application will be based onstructure IIb, with the proviso, that if the hydrogen on the pyrazolering is replaced by an alkyl group then it will be indicated if thecompound obtained is an isomeric mixture.

The compounds of the invention are illustrated and defined as follows:##STR5## wherein R₁ is hydrogen, alkyl (C₁ -C₃), benzyl, acyl (C₂ -C₄)or N-alkyl (C₁ -C₃) carboxamido; R₂ is hydrogen, methyl or phenyl; R₃ ismethyl or ##STR6## wherein X is hydrogen, halogen, alkyl (C₁ -C₃) andtrifluoromethyl; and salts thereof.

The invention also relates to a method for controlling undesirable plantspecies with the compounds III, above. The pyrazolyltriazole compoundsof the invention can be prepared by several procedures. One procedure,hereinafter referred to as procedure A, comprises, reacting anarylcyanoacetaldehyde (1) or an arylcyanoketone (2) with formylhydrazinein a molar ratio of 1:2 but preferably with an excess of formylhydrazine(1:2.5 to 1:3.0 molar ratio) in a melt at elevated temperatures of fromabout 150° C. to 250° C. and preferably 160° C. to 190° C. and areaction time from about 1 hour to about 5 hours. The reaction scheme ofprocedure A, reacting arylcyanoacetaldehyde (1) or arylcyanoketone (2)with formylhydrazine, is graphically illustrated as follows:

Procedure A ##STR7## On completion of the reaction the melt istriturated with a mixture of water and a chlorinated hydrocarbon toremove the unreacted starting materials which may be present. Theisolated crude product may then be further purified if necessary bystandard laboratory procedures, such as crystallizations,precipitations, chromatography and the like, all well known to thepractitioners of the art.

Another procedure which may be used to prepare the pyrazolyltriazolecompounds of the invention, hereinafter referred to as procedure B,comprises, reacting a substituted 3-aminopyrazole with asym-diformylhydrazine in a molar ratio of 1:1 to 1:3 in a high boilingpolar solvent, such as ethylene glycol, propylene glycol, diethyleneglycol, diethylene glycol monomethylether and the like at temperaturesfrom about 100° C. to 250° C. and preferably 150° C. to 190° C.Procedure B is graphically illustrated as follows:

Procedure B ##STR8##

On completion of the reaction the product may be isolated and purifiedby standard laboratory procedures, such as filtration, precipitation,crystallization, chromatography and the like.

The acid addition salts of the compounds of the present invention may beprepared by treating said compounds in an alcohol (C₁ -C₃) with theappropriate acid, evaporating the thus formed solution to dryness andrecovering the desired acid addition salt. Illustrative of the acidswhich are suitable for use in the present invention may be mentioned forexample, acids such as hydrochloric acid, hydrobromic acid, hydroiodicacid, sulfuric acid, hydrogen sulfate, methyl sulfate, nitric acid,phosphoric acid, perchloric acid, alkanoic (C₂ -C₄) acid, benzenesulfonic acid, p-toluene sulfonic acid and the like.

If desired, the compounds of the present invention may be acylated bystandard laboratory procedures using acid chlorides, or anhydrides suchas acetyl chloride, propionyl chloride, benzoyl chloride, aceticanhydride, propionic anhydride and the like. The compounds of thepresent invention may also be alkylated by the alkyl halides, alkylsulfates, alkyl toluenesulfonates and the like by standard laboratoryprocedures.

Among the compounds which can be prepared by one or both of the aboveprocedures are:

4-(4-Phenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-Phenyl-3-pyrazolyl)-b 4H-1,2,4-triazole hydrochloride;

4-(4-Phenyl-3-pyrazolyl)-4H-1,2,4-triazole nitrate;

4-(1-Acetyl-4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(1-Acetyl-4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole hydrochloride;

4-(4-Phenyl-1-propionyl-3-pyrazolyl)-4H-1,2,4-triazole

4-[1(2)-N-Methylcarboxamido-4-phenyl-3(5)pyrazolyl]-4H-1,2,4-triazole;

4-[1(2)-Methyl-4-phenyl-3(5)-pyrazolyl]-4H-1,2,4-triazole;

4-[1(2)-Benzyl-4-phenyl-3(5)-pyrazolyl]-4H-1,2,4-triazole;

4-(4-o-Tolyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-o-Tolyl-3-pyrazolyl)-4H-1,2,4-triazole hydrochloride;

4-(4-m-Tolyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-m-Tolyl-3-pyrazolyl)-4H-1,2,4-triazole hydrochloride;

4-(4-m-Chlorophenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-m-Chlorophenyl-5-methyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-p-Chlorophenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-m-Fluorophenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-p-Fluorophenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-[4-(α,α,α-Trifluoro-m-tolyl)-3-pyrazolyl]-4H-1,2,4-triazole;

4-(4-Methyl-5-phenyl-3-pyrazolyl)-4H-1,2,4-triazole;

4-(4-Methyl-5-phenyl-3-pyrazolyl)-4H-1,2,4-triazole hydrochloride.

The compounds of the present invention as represented and defined byformula III above are highly effective herbicidal agents. They areparticularly effective as selective preemergence herbicides applied at arate between 0.11 kg and 11.2 kg per hectare and preferably from 0.56 kgto 5.6 kg per hectare of active compound, and will control wild oats,crabgrass, foxtail, and barnyardgrass, and broadleaf weeds such asmustard, pigweed, velvetleaf and morningglory in the presence of cropssuch as corn, cotton, soybeans and rice.

The compounds of the present invention, as represented and defined byformula III above are also effective as postemergence herbicides appliedto the foliage of undesirable plants at a rate between about 1.1 kg to11.2 kg per hectare, and preferably from 1.1 kg to 5.6 kg per hectare.Used as postemergence herbicides, the compounds of the present inventiondisplay activities similar to those described under preemergence, i.e.at lower rates (as described above) they selectively control wild oats,crabgrass, foxtail, barnyardgrass, mustard, pigweed, velvetleaf andmorningglory in the presence of crops such as corn, cotton, soybean andrice.

The compounds of the present invention, when applied at high levels,will act as broad spectrum herbicides and thus may be used to eliminateall vegetation where this may be desirable.

For application of the formula III compounds and their salts as pre- andpostemergence herbicides, the compounds or their salts are generallyformulated as herbicidal compositions by admixing a suitable adjuvantwith a herbicidally effective amount of these compounds or their salts.Suitable adjuvants include one or more solid or liquid carriers,diluents and formulation aids, particularly surfactants.

The active compounds may be formulated as dusts, dust concentrates,granules, prills, wettable powders or emulsifiable concentrates.

Dusts are readily prepared by grinding together about 1 to 25% by weightof the active agent from about 99 to 75% by weight of a solid diluentsuch as kaolin, attapulgite, diatomaceous earth, or the like. Dustconcentrates are prepared in a similar fashion excepting that about 25to 95% by weight of the active agent is ground about 75 to 5% by weightof the diluent. Granules or prills may be prepared from the aboveformulations by standard industrial methods.

Wettable powders are prepared in the same manner as the dustconcentrates excepting that about 1 to 5% by weight of a dispersingagent such as sodium lignosulfonate, or the sodium salt of condensednaphthalene sulfonic acid is blended with the mixture and about 1 to 5%of a surfactant, such as polyoxyethylene ethanol is also blended withthe formulation. In practice the powder is mixed with water and appliedto the plant foliage as an aqueous spray.

Emulsifiable concentrates are prepared by dissolving from 15 to 70% ofthe compound in 85 to 30% of a water-miscible solvent, such as wateritself or another polar water-miscible solvent, such as 2-methoxyethanol, methanol, propylene glycol, diethylene glycol, diethyleneglycol monomethyl ether, formamide, and methylformamide, wherein saidconcentrates contain 1 to 5% of a surfactant, such as TWEEN® 20, apolyoxyethylene sorbitan monolaurate surfactant by Atlas ChemicalIndustries, or the like. Application of the material is made by adding apredetermined quantity to a spray tank and applying the concentrate assuch or in combination with an additional quantity of water or otherpolar solvent as a liquid spray.

The present invention is further illustrated by the examples set forthbelow. These examples are provided only by way of illustration and arenot intended to be limiting on the invention.

EXAMPLE 1 Preparation of 4-(4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole,Method A

An integral mixture of β-hydroxy-α-phenylacrylonitrile (5 g) andformylhydrazine (10 g ) is heated in an oil bath at 170° C to 180° C.The melt is stirred and heated for 3 hours. It is then cooled, water (50ml) and chloroform (50 ml) is added and the mixture stirred. The solidis collected by filtration and recrystallized from a mixture ofmethanol/dimethylsulfoxide, m.p. 271° C to 274° C (dec).

EXAMPLE 2 Preparation of 4-(4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole,Method B

A slurry of 3-amino-4-phenylpyrazole (1.6 g, 0.01 mole) andsym-diformylhydrazine (2.2 g, 0.025 mole) in ethylene glycol (10 ml) isprepared and heated slowly to 80° C, at which point a clear solution isobtained. Heating is continued to 150° C and the solution held at 150° Cto 180° C for 3 hours. The mixture is then cooled to 60° C and filteredto give 1.3 g of product. A second fraction of 0.3 g is obtained bydiluting the filtrate with water. Both fractions are identical to theproduct of Example 1. The combined yield is 76%.

EXAMPLE 3 Preparation of 4-(4-phenyl-3-pyrazolyl)-4H-1,2,4-triazolehydrochloride

A suspension of 4-(4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole (1.75 g) inmethanol (25 ml) and water (10 ml) is stirred and concentratedhydrochloric acid until a clear solution is obtained. The solvent isremoved and the residue recrystallized from methanol/ether at -10° CYield 1.7 g (90%), mp. 210° C to 216° C (dec).

EXAMPLE 4-16

By the procedure of Example 1, (Method A) the following compounds, andby the procedure of Example III their acid addition salts, are preparedcorresponding to formula III. ##STR9##

                  Table I                                                         ______________________________________                                        Ex-                                                                           peri-                                                                         ment                                                                          No.  R.sub.1                                                                             R.sub.2 R.sub.3   Acid    m.p.                                     ______________________________________                                        4    H     H       phenyl    HNO.sub.3                                                                           158° C-160° C                5    H     H       p-Chlorophenyl  257° C-260° C                6    H     H       m-Chlorophenyl  203° C-205° C                7    H     H       p-Fluorophenyl                                             8    H     H       m-Fluorophenyl  235° C-238° C                9    H     H       o-tolyl         202° C-205° C                10   H     H       o-tolyl   HCl   145° C-150° C                11   H     H       m-tolyl         198° C-201° C                12   H     H       m-tolyl   HCl   215° C-220° C (dec)          13   H     CH.sub.3                                                                              m-Chlorophenyl  275° C-278° C                14   H     H       α,α,α-trifluoro-                                                            224° C-226° C                                   m-tolyl                                                    15   H     phenyl  methyl          235° C-238° C                16   H     phenyl  methyl    HCl   215° C-220° C                ______________________________________                                                                           (dec)                                  

EXAMPLE 17 Preparation of4-[182)-Methyl-4-phenyl-3(5)-pyrazolyl]-4H-1,2,4-triazole (isomericmixture)

4-(4-Phenyl-3-pyrazolyl)-4H-1,2,4-triazole (31.6 g, 0.15 mole) is addedto a solution of sodium methoxide (8.0 g, 0.15 mole) in absolutemethanol (175 ml.). The mixture is then heated to 55° C for 1/2 hour anddimethyl sulfate added dropwise. After the addition is complete, thereaction mixture is heated at reflux for 5 hours. The methanol isremoved in vacuo and the residual yellow solid extracted with boilingbenzene. The benzene solution is treated with charcoal, filtered andcooled. The separated white crystalline solid is filtered and dried invacuo. Yield 28 g (83%), m.p. 131° C to 135°0 C.

Analysis calculated: C, 63.98; H, 4.92; N, 31.09. Found: C, 63.83; H4.89; N, 31.09.

The isomeric mixture of the 1(2)-benzyl derivative is prepared by theabove procedure using sodium bicarbonate as an acid binder andbenzylbromide instead of dimethyl sulfate, m.p. 151° C to 154° C.

EXAMPLE 18 Preparation of4-(1-Acetyl-4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole

A suspension of 4-(4-phenyl-5-pyrazolyl)-4H-1,2,4-triazole (1.0 g) inacetic anhydride is refluxed until a clear solution is obtained. Thesolution is poured into ice water and stirred for 1/2 hour. Theyellowish solid is collected and recrystallized from a mixture ofchloroform/hexane, giving a white powder, m.p. 165° C to 168° C.Similarly prepared is the propionyl derivative.

EXAMPLE 19 Preparation of 4-[1(2)-N-Methylcarboxamido-4-phenyl3(5)-pyrazolyl]-4H-1,2,4-triazole (isomeric mixture)

To a solution of 4(4-phenyl-3-pyrazolyl)-4H-1,2,4-triazole in drydimethylformamide (50 ml) at 150° C. Triethylamine (50 mg) is added andafter a few minutes, a white solid begins to form. The reaction mixtureis stirred for 18 hours at room temperature. It is then cooled to 15° C,filtered, the isolated solid washed well with water. Crystallizationfrom methanol yields 2.0 g (77%) of white crystals, m.p. 222° C to 225°C.

Analysis calculated: C, 58.19; H, 4.51; N, 31.32. Found: C, 58.06; H,4.63; N, 31.32.

EXAMPLE 20

The preemergence activity of the compounds of the present invention isdemonstrated by the following tests, wherein a 50/50 acetone/water (v/v)mixture and sufficient test compound to provide the amount per hectareof said compound as indicated in Table II when the mixture is applied topots planted with seeds or propagules of test plant species.

The pots are prepared the day of herbicide treatment by putting 100 mlof soil in each plastic pot as a base, then morningglory and wild oatseeds are placed on this base and covered with 50 ml (1 cm to 1.37 cm)of soil. Seeds of the other 8 plant species identified below areseparately mixed with soil and 50 ml of the soil seed mix added to thepot. The pots are then tamped lightly to level the soil and the soil iswetted with water prior to herbicide application. This prewettinginsures that the subsequently applied heribicide treatment solutionspreads evenly over the surface of the pot and protects the weed seedsfrom acetone injury. Each of the 10 weed species is contained in aseparate pot. The pots are then arranged in 25.4 × 30.4 cm flats priorto chemical treatment.

The planted pots are treated with 5 ml of test solution and then placedon benches in the greenhouse. Pots are watered after treatemtn as neededand held in the greenhouse for 3 weeks at which time the results arerecorded, as reported in Table II.

Plant Species Used in Preemergence Herbicide Evaluation

    ______________________________________                                        Common Name                                                                              Abbreviation                                                                             Scientific Name                                         ______________________________________                                        Lambsquarters                                                                            LA         Chenopdium album                                        Wild Mustard                                                                             MU         Brassica kaber                                          Pigweed    PI         Amaranthus retroflexus                                  Ragweed    RW         Ambrosia artemisiifolia                                 Morningglory                                                                             MG         Ipomoea purpurea                                        Barnyardgrass                                                                            BA         Echinochloa crusgalli                                   Crabgrass  CR         Digitaria sanguinalis                                   Green Foxtail                                                                            FO         Setaria viridis                                         Wild Oats  WO         Avena fatua                                             Velvetleaf VL         Abutilon theophrasti                                    Corn       CN         Zea mays                                                Cotton     CO         Gossypium virsutum                                      Soybeams   SY         Glycine max                                             Rice       RI         Oryza sativa                                            ______________________________________                                    

The rating system used in the evaluation of the experimental data isgiven below:

    ______________________________________                                                            % Difference in growth                                    Rating System       from check*                                               ______________________________________                                        0 - No effect       0                                                         1 - Possible effect  1-10                                                     2 - Slight effect   11-25                                                     3 - Moderate effect 26-40                                                     5 - Definite injury 41-60                                                     6 - Herbicidal effect                                                                             61-75                                                     7 - Good herbicidal effect                                                                        76-90                                                     8 - Approaching complete kill                                                                     91-99                                                     9 - Complete kill   100                                                       4 - Abnormal growth, that is, a definite physiological                        malformation but with an over all effect less than 5                          on the rating scale.                                                          ______________________________________                                         *Based on visual determination of stand, size, vigor, chlorosis, growth       malformation and over-all plant appearance.                              

                                      TABLE II                                    __________________________________________________________________________    Preemergence Herbicidal Activity                                                                 Treat-                                                                        ment                                                       Compound           kg/ha                                                                             LA MU PI                                                                              RW MG BA CR FO WO VL CN CO SY                                                                              RI                __________________________________________________________________________    4-(4-p-Chlorophenyl-3-pyrazolyl)-                                                                11.2                                                                              9  9  9 9  0  0  0  0  0  7                            4H-1,2,4-triazole                                                             4-(4-Phenyl-3-pyrazolyl-4H-1,2,4-                                                                5.6 9  9  9 9  9  9  9  9  9  9                            triazole . HCl                                                                4-(4-Phenyl-3-pyrazolyl-4H-1,2,4-                                                                4.5.sup.1                                                                         9  9  9 9  7  9  9  9  9  9  8  9  9 8                 triazole                                                                      4-(4-Phenyl-3-pyrazolyl-4H-1,2,4-                                                                0.56.sup.2                                                                        9  9  9 9  5  9  9  8  5  8  2  3  5 1.5               triazole                                                                      4-(4-Phenyl-3-pyrazolyl-4H-1,2,4-                                                                0.28.sup.3                                                                        9  9  9 7  3  5  7  8  2  5  1  1  1 0                 triazole                                                                      4-(4-Phenyl-3-pyrazolyl-4H-1,2,4-                                                                0.145.sup.4                                                                       9  8  9 6  1  3  5  6  1  5  0  0  0 0                 triazole                                                                      4-(1-Acetyl-4-phenyl-3-pyrazolyl)-                                                               4.5 9  9  9 9  9  9  9  9  9  9  9  9  9 9                 4H-1,2,4-triazole                                                             4-(1-Acetyl-4-phenyl-3-pyrazolyl)-                                                               0.28                                                                              9  8  9 9  9  5  6  9  1  3  2  0  0 0                 4H-1,2,4-triazole                                                             4-(1-Acetyl-4-phenyl-3-pyrazolyl)-                                                               5.6 9  9  9 9  9  9  9  9  9  9                            4H-1,2,4-triazole . HCl                                                       4-(4-p-Fluorophenyl-3-pyrazolyl-                                                                 4.5 9  9  9 9  9  6  8  8  5  9  1  3  2 3                 4H-1,2,4-triazole                                                             4-(4-p-Fluorophenyl-3-pyrazolyl-                                                                 0.56                                                                              9  9  9 5  0  0  0  0  0  0  0  0  0 0                 4H-1,2,4-triazole                                                             4-(4-Methyl-5-phenyl-3-pyrazolyl-                                                                10.1                                                                              2  7  7 7  2  2  8  8  2  2  0  0  0 1                 4H-1,2,4-triazole                                                             4-(4-Methyl-5-phenyl-3-pyrazolyl-                                                                3.35                                                                              0  7  5 6  1  1  7  7  0  0  0  0  0 0                 4H-1,2,4-triazole                                                             4-(4-o-Tolyl-3-pyrazolyl)-4H-1,2,4-                                                              5.6 9  9  9 7  0  0  7  7  0  9                            triazole                                                                      4-(4-m-Tolyl-3-pyrazolyl)-4H-1,2,4-                                                              4.5 9  9  9 9  0  6  9  9  6  9  5  0  0 1                 triazole                                                                      4-(4-m-Tolyl-3-pyrazolyl)-4H-1,2,4-                                                              1.12                                                                              9  9  9 9  0  0  0  0  0  0  0  0  0 0                 triazole                                                                      4-(4-m-Chlorophenyl-5-methyl-3-                                                                  5.6 8  9  8 9  0  0  0  0  0  0                            pyrazolyl)-4H-1,2,4-triazole                                                  4-(4-m-Tolyl-3-pyrazolyl)-4H-                                                                    11.2                                                                              9  9  9 9  0  7  9  9  6  9                            1,2,4-triazole . HCl                                                          4-(4-o-Tolyl-3-pyrazolyl)-4H-                                                                    5.6 9  9  9 0  0  0  6  0  5  8                            1,2,4-triazole . HCl                                                          4-(4-Methyl-5-phenyl-3-pyrazolyl)-                                                               11.2                                                                              0  8  8 7  2  0  8  8  1  2                            4H-1,2,4-triazole . HCl                                                       4-(4-m-Chlorophenyl-3-pyrazolyl)-                                                                11.2                                                                              9  9  9 9  9  5  7  7  6  3                            4H-1,2,4-triazole                                                             4-(4-m-Chlorophenyl-3-pyrazolyl)-                                                                4.5 9  9  7 9  0  0  0  0  0  0  0  0  0 0                 4H-1,2,4-triazole                                                             4-(4-m-Fluorophenyl-3-pyrazolyl)-                                                                4.5 9  9  9 9  9  9  9  9  9  9  5  0  0 0                 4H-1,2,4-triazole                                                             4-(4-m-Fluorophenyl-3-pyrazolyl)-                                                                0.56                                                                              9  7  8 9  0  0  0  1  0  2  0  0  0 0                 4H-1,2,4-triazole                                                             4-(1(2)-Methyl-4-phenyl-3-pyrazolyl)-                                                            4.5 9  9  9 9  9  6  9  9  5  8  5  5  6 1                 4H-1,2,4-triazole-isomeric mixture                                            4-(1(2)-Methyl-4-phenyl-3-pyrazolyl)-                                                            1.12                                                                              8  2  8 9  5  0  1  2  0  2  2  0  0 0                 4H-1,2,4-triazole-isomeric mixture                                            4-(1(2)-Benzyl-4-phenyl-3-pyrazolyl)-                                                            4.5 9  9  9 8  2  7  9  8  5  8  1  0  1 1                 4H-1,2,4-triazole-isomeric mixture                                            4-(1(2)-Benzyl-4-phenyl-3-pyrazolyl)-                                                            1.12                                                                              8  1  8 2  0  5  6  6  0  0  1  0  0 0                 4H-1,2,4-triazole-isomeric mixture                                            4-(1-Propionyl-4-phenyl-3-pyrazolyl)-                                                            4.5 9  9  9 9  9  9  9  9  9  9  9  9  9 9                 4H-1,2,4-triazole                                                             4-(1-Propionyl-4-phenyl-3-pyrazolyl)-                                                            1.12                                                                              9  9  9 9  9  9  9  9  9  9  9  7  9 3                 4H-1,2,4-triazole                                                             4-(1-Propionyl-4-phenyl-3-pyrazolyl)-                                                            0.28                                                                              9  9  9 9  3  5  7  9  0  6  2  0  0 0                 4H-1,2,4-triazole                                                             4-(4-m-Trifluoromethylphenyl-3-                                                                  4.5    9  9 8  3  8  9  7  5  7  6  3  3 7                 4H-1,2,4-triazole                                                             4-(4-Phenyl-3-pyrazolyl)-4H-1,2,4-                                                               4.5 9  9  9 9  2  9  9  9  9  9  6  9  9 8                 triazole . HNO.sub.3                                                          4-(4-Phenyl-3-pyrazolyl)-4H-1,2,4-                                                               0.56                                                                              9  9  9 0  0  7  9  8  1  5  0  0  1 2                 triazole . NHO.sub.3                                                          4-(4-m-Trifluoromethylphenyl-3-                                                                  1.12   9  9 1  1  2  8  1  1  0  2  0  0 1                 pyrazolyl)-4H-1,2,4-triazole                                                  4-(1(2)-N-Methylcarboxamide-4-                                                                   11.2   9  8 5  3  8  9  8  0  5                            phenyl-3-pyrazolyl)-4H-1,2,4-                                                 triazole . isomeric mixture                                                   __________________________________________________________________________     .sup.1 Average of 4 Replicates                                                .sup.2 Average of 6 Replicates                                                .sup.3 Average of 6 Replicates                                                .sup.4 Average of 5 Replicates                                           

EXAMPLE 21

The postemergence herbicidal activity of the compounds of the presentinvention is demonstrated by the following tests, wherein a variety ofmonocotyledonous and dictoyledonous plants are treated with testcompounds dispersed in aqueous acetone mixtures. In the tests, seedlingplants are grown in jiffy flats for about 2 weeks. The test compoundsare dispersed in 50/50 acetone/water (v/v) mixtures containing 0.5%TWEEN® 20, a polyoxyethylene (20) sorbitan monolaurate surfactant byAtlas Chemical Industries, in sufficient quantity to provide the amountper hectare of active compound as indicated in Table III when applied tothe plants through a spray nozzle operating at 2.8 kg per cm² pressurefor a predetermined time. After spraying, the plants are placed ongreenhouse benches and cared for in the usual manner, commensurate withconventional greenhouse practices. Two weeks after treatment, theseeding plants are examined and rated according to the rating systemprovided in Example 20.

The plant species used in the postemergence herbicide activityevaluation are the same as those used in the preemergence herbicideevaluation test and are listed in Example 20. The results are reportedin Table III.

                                      Table III                                   __________________________________________________________________________    Postemergence Herbicidal Activity                                                                Treat-                                                                        ment                                                       Compound           kg/ha                                                                             LA MU PI                                                                              RW MG BA CR FO WO VL CN CO WY                                                                              RI                __________________________________________________________________________    4-(4-Phenyl-3-pyrazolyl)-4H-                                                                     5.6 9  9  9 9  8  8  8  7  7  6                            1,2,4-triazole . HCl                                                          4-(4-Phenyl-3-pyrazolyl)-4H-                                                                     4.5.sup.1                                                                         9  8  9 5  8  6  7  5     5  3  5  6 1                 1,2,4-triazole                                                                4-(4-Phenyl-3-pyrazolyl)-4H-                                                                     2.24.sup.2                                                                        8  6  8 2  7  2  3  0  0  3  5  7  7 0                 1,2,4-triazole                                                                4-(1-Acetyl-4-phenyl-3-pyrazolyl)-                                                               4.5 8  8  9 0  7  0  1  1  0  2  5  8  7 0                 4H-1,2,4-triazole                                                             4-(1-Acetyl-4-phenyl-3-pyrazolyl)-                                                               5.6 9  9  9 9  7  8  2  6  8  5                            4H-1,2,4-triazole . HCl                                                       4-(4-p-Fluorophenyl-3-pyrazolyl)-                                                                4.5 9  8  9 2  3  3  0  0  0  9  0  1  3 0                 4H-1,2,4-triazole                                                             4-(4-p-Fluorophenyl-3-pyrazolyl)-                                                                1.12                                                                              7  5  9 1  1  0  0  0  0  7  0  1  3 0                 4H-1,2,4-triazole                                                             4-(4-o-Tolyl-3-pyrazolyl)-4H-                                                                    5.6 9  9  7 0  0  0  0  0  0  0                            1,2,4-triazole                                                                4-(4-m-Tolyl-3-pyrazolyl)-4H-                                                                    4.5 7  9  9 5  7  0  1  0  0  1  1  3  5 0                 1,2,4-triazole                                                                4-(4-m-Tolyl-3-pyrazolyl)-4H-                                                                    11.2                                                                              9  9  7 5  1  1  1  1  7  5                            1,2,4-triazole . HCl                                                          4-(4-m-Chlorophenyl-3-pyrazolyl)-                                                                11.2                                                                              9  9  5 0  0  1  1  1  0  0                            4H-1,2,4-triazole                                                             4-(4-m-Fluorophenyl-3-pyrazolyl)-                                                                11.2                                                                              8  9  9 9  5  7  6  6  9  5                            4H-1,2,4-triazole                                                             4-(4-Phenyl-3-pyrazolyl)-4H-                                                                     11.2                                                                              9  9  9 9  9  9  9  9  9  9                            1,2,4-triazole . HNO.sub.3                                                    4-(4-Phenyl-3-pyrazolyl)-4H-                                                                     1.12                                                                              9  9  9 2  8  0  2  0  0  5  0  6  5 0                 1,2,4-triazole . HNO                                                          4-(1(2)-Methyl-4-phenyl-3-pyra-                                                                  11.2                                                                              9  4  6 0  4  0  0  0  0  2                            zolyl)-4H-1,2,4-triazole-                                                     isomeric mixture                                                              4-(1(2)-Benzyl-4-phenyl-3-pyrazolyl)-                                                            1.12                                                                              9  5  5 0  5  0  0  0  0  0                            4H-1,2,4-triazole, isomeric mixture                                           4-(1-Propionyl-4-phenyl-3-pyra-                                                                  11.2                                                                              9  7  6 1  8  8  7  7  9  8                            zolyl)-4H-1,2,4-triazole                                                      4(1-Propionyl-4-phenyl-3-pyra-                                                                   1.12                                                                              7  5  7 0  4  4  0  0  5  5  0  7  7 2                 zolyl)-4H-1,2,4-triazole -4(4-m-Trifluoromethylphenyl-3-                                         11.2                                                                              7  6  8 2  7  2  1  1  0  2                            pyrazolyl)-4H-1,2,4-triazole                                                  __________________________________________________________________________     .sup.1 Average of 5 Replicate                                                 .sup.2 Average of 2 Replicate                                            

EXAMPLE 22

The aquatic herbicidal activity of the compounds of the presentinvention is compared to a commercial herbicide:2-chloro-4-ethylamino-6-isopropylamino-s-triazine, using aquatic weedsas target organisms in the following test, wherein a 50/50 acetone/water(v/v) mixture and sufficient test compound are used to provide theamount per hectare of the compound as indicated in Table IV when themixture is applied to 5 inch dixie cups planted with propagules of testplant species.

Method

The six species of aquatic weeds:

    ______________________________________                                        Alligator weed                                                                           AW        (Alternanthera philoxeroides)                            Parrot's feather                                                                         PF        (Myriophyllum brasiliense)                               Water hyacinths                                                                          WH        (Eichhornia crassipes)                                   Duck weed  DW        (Lemna minor)                                            Salminia   SAL       (Salminia auriculata)                                    Water lettuce                                                                            WL        (Pistia stratiotes)                                      ______________________________________                                    

are prepared as follows:

1. Cuttings of alligator weed and parrot's feathers are taken from stockcultures and are set to root in a vermiculite:sand-PERLITE® (1:1:1) mixin shallow flats. A week later, the rooted cuttings are transferred to 5inch dixie cups 1/2 filled with coarse sand. The cups are filled toflooding with water and placed in aluminum baking pans.

2. At the same time, the above-rotted cuttings are set in cups, a singlepropagule of water hyacinth and of water lettuce consisting of stolon,petiole and leafamine are placed in water-filled cups.

3. Also at the same time, enough duck weed and Salminia are transferredfrom the pond table to their respective cups to cover the surface, andthe cups are placed in the aluminum baking pans.

4. The pans with their six cups are placed in the greenhouse and kept ata constant water level and are maintained 4 days prior to spraying.

The plants are sprayed on the fifth day with the test solutionscontaining the active ingredients in the amounts indicated in Table IVand held in the greenhouse for four weeks. Results are recorded at twoand at four weeks as reported in Table IV.

                                      Table IV                                    __________________________________________________________________________    Aquatic Herbicidal Activity of a Compound of the Present Invention            as Compared to a Commercial Herbicide: 2-Chloro-4-ethylamino-                 6-isopropylamino-s-triazine at the Indicated Rates.                           Two weeks' data, except as indicated.                                         Compound                                                                           kg/Hectare      AW PF WH DW SAL WL                                       __________________________________________________________________________    2-Chloro-4-ethylamino-                                                                       4.48  9  9  9  9  9   9                                         6-isopropylamino-                                                                           1.12  9  9  9  9  9   9                                         s-triazine    0.56  8  9  9  9  9   9                                                       0.28  8  8  9  9  9   9                                        4-(4-Phenyl-5-pyrazolyl)-                                                                    4.48  9  8  7  9  5   9                                         4H-1,2,4-triazole      9* 8*                                                                1.12  9  7  2  9  5   9                                                                9* 7*                                                                0.56  9  3  2  9  5   9                                                                8* 5*                                                                0.28  9  3  1  9  5   9                                                                7* 2*                                                 __________________________________________________________________________     *Four weeks' data.                                                       

We claim:
 1. A method for the control of undesirable plant species,comprising contacting the undesirable plant species, seeds or propagulesthereof, with a herbicidally effective amount of a compound of theformula: ##STR10## wherein R₁ is hydrogen, alkyl (C₁ -C₃), benzyl, acylRCO wherein R is C₁ -C₃ alkyl or N-alkyl (C₁ -C₃) carboxamido; R₂ ishydrogen, methyl or phenyl; R₃ is methyl of ##STR11## wherein X ishydrogen, halogen, alkyl (C₁ -C₃) or CF₃, and the acid addition salt ofthe compound wherein the acid is HCl, HBr, HI, HNO₃, H₂ SO₄, HSO₄ ⁻, CH₃OSO₂ O⁻, H₃ PO₄, HClO₃, alkanoic (C₂ -C₄) acid, benzene sulfonic acid,or p-toluene sulfonic acid.
 2. A method according to claim 1 wherein R₁and R₂ of the formula are each hydrogen.
 3. A method according to claim1 wherein R₁ of the formula is methyl or benzyl; R₂ is hydrogen; and R₃is phenyl; and wherein the compound is an isomeric mixture.
 4. A methodaccording to claim 1 wherein R₁ is acetyl, propionyl orN-methylcarboxamido; R₂ is hydrogen; And R₃ is phenyl.
 5. A methodaccording to claim 1, comprising, contacting the undesirable plantspecies or seeds thereof with the compound in an amount sufficient toprovide from 0.11 kg to 11.2 kg per hectare of the compound.